The production of eggs is energetically expensive in terms of calories and time, whereas sperm production is less so.

“Making eggs is expensive calorically and in terms of time and calories, it they're expensive and organisms. So, what we are designed to do is convert energy into offspring. That's basically what evolution uh put us here to do. And you want to do that as efficiently as possible. >> So eggs are energetically expensive. Sperm is less energy energetically expensive.”